Pressure differential indicator with fire stop

ABSTRACT

An across the wall pressure differential indicating apparatus comprising a wall duct having first and second open ends, first and second mounting plates respectively attached to the wall duct at the first and second open ends respectively, a low speed airflow indicator adapted to indicate a pressure differential and mounted in fluid communication with the wall duct such that substantially, all airflow passing through the wall duct also passes through the indicator, and an intumescent material disposed in the wall duct between the first and second ends.

FIELD OF THE INVENTION

This invention relates to pressure differential indicators for firerated walls. More particularly, this invention related to pressuredifferential indicators with an intumescent material or a door or bothfor fire rated walls.

BACKGROUND OF THE INVENTION

Some specific spaces or rooms such as at a hospital require a propernegative or positive pressure in the interior space or room in order toprevent germs or virus dissipating through a fissure by airflow to anexterior space outside the room such as an exterior room, hallway orcorridor. The interior air pressure is lower than that at the exteriorbecause airflow travels from a space of higher pressure to a space oflower pressure. It is well known to provide a device that keeps theinterior air pressure lower than that of the exterior in order tomaintain a clean and healthy environment, such a system is described inU.S. Pat. No. 5,228,306. It is necessary for the doctors, nurses, andother concerned employees and individuals to easily monitor whether ornot a proper vacuum (a negative pressure differential) is beingmaintained in a room from outside the room such as in the hallway orcorridor. Fairly sophisticated devices, usually electronicallycontrolled, have been developed for this purpose. However, these devicesare expensive to procure and maintain and subject to failure.Furthermore, because the pressure differential across such walls,particularly hospital walls, is very small, present day devices areexpensive and difficult to maintain and calibrate.

A pressure differential indicating apparatus, which incorporates apreferably adjustable airflow duct across the wall between the low andhigh pressure spaces and a low airflow indicator on the side of the wallopposite the space that is to be monitored to indicate air pressuredifferentials and particularly low pressure differentials across wallsis disclosed in U.S. Pat. No. 5,589,643 which issued Dec. 31, 1996 andis incorporated herein by reference in its entirety.

One conventional air velocity measuring device uses a hot wireanemometer, which requires electrical power to operate and is expensive.A relatively less expensive mechanical device, a rotational vane typethat has a number of intricate moving parts that require maintenance, isstill relatively expensive and is not easy to monitor by a personwalking down a hospital hall.

When the pressure differential indicating apparatus referenced U.S. Pat.No. 5,589,643 is placed in a fire rated wall, such as found in manyhospitals and other buildings, it too must be fire rated. One method ofproviding a fire rated pressure differential indicating apparatus is toincorporate an intumescent material in the apparatus. Another method isto provide a door that is typically in the closed position and is openedto take a pressure differential measurement.

SUMMARY OF THE INVENTION

This invention relates to an across the wall pressure differentialindicating apparatus comprising a wall duct having first and second openends, first and second mounting plates respectively attached to the wallduct at the first and second open ends respectively, a low speed airflowindicator adapted to indicate a pressure differential and mounted influid communication with the wall duct such that substantially allairflow passing through the wall duct also passes through the indicator,and an intumescent material disposed in the wall duct between the firstand second ends.

This invention also relates to an across the wall pressure differentialindicating apparatus comprising a wall duct having first and second openends, first and second mounting plates respectively attached to the wallduct at the first and second open ends respectively, a low speed airflowindicator adapted to indicate a pressure differential and mounted influid communication with the wall duct such that substantially allairflow passing through the wall duct also passes through the indicator,and a door disposed on the wall duct for limiting airflow through thewall duct.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a room and a pressure differentialindicator with an exemplary embodiment of the present invention mountedon the wall.

FIG. 2 is an enlarged perspective view of the pressure differentialindicator illustrated in FIG. 1.

FIG. 2A is a frontal view along 2A-2A of a mounting plate of theapparatus in FIG. 2.

FIG. 3 is a perspective view another embodiment having an intumescentfire stop in the pressure differential indicator.

FIG. 4 is a detailed perspective view of a first section of the pressuredifferential indicator having the intumescent fire stop.

FIG. 5 is a perspective view of another embodiment of a pressuredifferential indicator having a slideable door.

DETAILED DESCRIPTION OF THE INVENTION

Illustrated in FIG. 1 is an exemplary embodiment of a pressuredifferential indicating apparatus 10 having a low speed airflowindicator 12 adapted to indicate a pressure differential across a wall14 of a room 16. The pressure differential indicating apparatus 10 isoperably mounted so that the indicator 12 is positioned on the wall 14outside of the room 16 at an easily observable level L (eye level orother) above the floor 13 of a corridor 17. The room 16 is typical ofone often found in a hospital which requires a proper negative pressurein the interior space or room 16 in order to prevent germs or virusdissipating through a fissure 11 such as may be found under a room door9 by airflow to an exterior space outside the room such as an exteriorroom, hallway, or corridor 17. The interior air pressure indicated by P1is lower than that of the exterior air pressure P2 because airflowtravels from a space of higher pressure to a space of lower pressure.

Referring now to FIG. 2, the pressure differential indicating apparatus10 includes a wall duct 18 to which the low speed airflow indicator 12mounted in operable fluid communication such that at least a portion ofthe airflow passing through the wall duct also passes through theindicator. Additionally, substantially all or all of the airflow passingthrough the wall duct also passes through the indicator. The wall duct18 has first and second open ends 20 and 22, respectively, which arecorrespondingly disposed through a hole 23 which extends through thewall 14. Flange like first and second mounting plates 30 and 32,respectively, having apertures 33 are connected to the first and secondopen ends 20 and 22 of the wall duct 18 and mounted to oppositely facingfirst and second sides 26 and 28, respectively, of the wall 14. Theplates are attached to the ends in a flange like fashion surrounding thefirst and second open ends 20 and 22 such to allow unrestricted airflowto pass through the first and second open ends 20 and 22. The airflowindicator 12 is mounted on a side of the second mounting plate 32opposite that by which the second mounting plate is mounted to the wall14 such that all airflow passing through the wall duct 18 also passesthrough the indicator. Referring briefly to FIG. 2A, a screen 37 may beplaced over the apertures 33 shown as the one on the room side of thewall 14, on the first open end 20.

The wall duct 18 may be an adjustable length wall duct having twosections, a first section 36 attached to the first mounting plate 30 anda second section 38 attached to the second mounting plate 32. One of thetwo sections is constructed so as to be slidingly disposed in and insealing engagement with the other of the two sections. The first section36 is slidingly disposed in and in sealing engagement with the secondsection 38. The second section 38 may include an extension 39 to providea convenient casing into which the indicator 12 may be mounted. Theextension 39 may be made of plexiglass or other material through which avane 62 of the indicator 12 may be seen. The first section 36 and secondsection 38 of the wall duct 18 may be made from steel, stainless steel,or other material able to withstand temperatures it would be exposed toin a fire. The indicator 12 can be mounted by screws 44 or some othermeans of attachment to the second section 38 and the indicator 12 mayinclude bubble levels 45 to help mount the entire apparatus and adjustthe indicator parallel to the floor. The wall duct 18 provides an airwaybetween the inside and outside of the room in order to develop a lowspeed airflow from the higher pressure area in the hallway outside theroom to the lower pressure area inside the room.

The airflow indicator 12 includes a housing 46 having front, back, top,bottom, left, and right wall portions 48A-48F, respectively, defining arectangular draft way 50 extending therethrough. The front wall portion48A has an inlet port 52 and the back wall portion 48B has a draftoutlet port 54 and the approximate size of the draft way 50. Theelongated vane 62 is suspended pendulum fashion from an upper portion 64of the housing 46 adjacent to the inlet port 52 and is disposedperpendicular to the left and right wall portions 48E and 48F andtransversely of the draft way 50. The vane 62 is pivotally mountedadjacent its upper end for free swinging movement between an at restvertically disposed position for zero airflow through the way to aninclined position angled in the direction of airflow, indicated by arrow53, through the way for airflow that is induced through the way by apressure differential across the wall 14. The vane 62 is proportioned tosubstantially close off the way when the vane is in its vertical at restposition and the vane, preferably, is a length of stripping of filmthickness dimensions. The strip may have indentation means extendinglongitudinally thereof for holding the strip against flexure. DwyerInstruments, Inc. in Indiana is a commercial vendor that can supply suchan indicator, suitable for use in the present invention, and based on anAir Velocity Gauge disclosed in U.S. Pat. No. 4,154,101.

The airflow indicator 12 is mounted such that the front wall portion 48Aand its draft outlet port 54 abuts or is close to the second mountingplate 32. A first cross-sectional area of the wall duct 18 as defined bya first width W1 and first height H1 of the rectangular wall duct issubstantially greater than a second cross-sectional area of the draftoutlet port 54 as defined by a second width W2 and a second height H2.Typically, H1 is about two times W1 and H2 is two times W2, but otherratios may be used. This assists in providing an unrestricted area foran airflow indicative of the pressure differential across the wall todevelop. Mounting the airflow indicator 12 in a clear plastic ductallows for ease of use and manufacture because the airflow indicator 12may be reversed such that the inlet port 52 and vane 62 are positionedclose to the second mounting plate 32 and its aperture 33 if one wantedthe apparatus to indicate a positive pressure differential across thewall 14 as opposed to a negative pressure differential or pressure dropacross the wall with respect to an observer outside the room 16.

A face plate 80 is mounted in the housing and has an arcuate slot 84 toform a window for viewing the position of vane, The face plate 80 hasmarkings to indicate the desired pressure drop or range. It need not becalibrated or gauged. This provides an easily read indicator forinforming observers passing by that sufficient pressure drop existsacross the wall and that equipment designed to maintain the pressuredrop is operating.

In another embodiment, shown in FIG. 3, disposed in a duct portion 35 ofthe first section 36 is an intumescent material 102. Intumescentmaterials swell when exposed to heat, and thus can be used in passivefire protection. Here, when the intumescent material 102 is exposed toheat, such as a fire, it swells to fill the aperture 33, thus preventingsmoke or fire from passing through the duct portion 35. The intumescentmaterial could also be located in draftway 50 of the housing 46. Onetype of intumescent material that may be used is 3M® Expantrol™ FlexibleIntumescent Strip E-FIS. Other types of intumescent materials may alsobe used. FIG. 4 is another view of first section 36 showing theintumescent material 102.

In another embodiment, shown in FIG. 5, a slideable door 104 is retainedby a first guide 106 and a second guide 108 against the housing 46 toblock flow through the inlet port 52 and the draft way 50. Typically,the default position for the door is in the closed position, as shown inFIG. 5. When the door 104 is in the closed position, in the event of afire, smoke, or chemical emergency in the corridor, it prevents air,gasses, smoke, or fire from passing from the corridor 17 through thedraftway 50 and into the room 16. If there is a fire, smoke, or chemicalemergency in the room 16, it prevents air, gasses, smoke, or fire frompassing from the room 16 through the draftway 50 and into the corridor17. The slideable door 104 has a protrusion 110 to allow an operator, byhand or with a reaching device such as a rod, to slide the door upwardlyin the direction of arrow 112 to allow air to flow through the draftway50 to measure airflow with the air speed indicator 12. Typically, thedoor will fall back in the direction of arrow 114 to a closed positionwhen the operator releases the protrusion. Instead of a slideable door,a door with a hinge may also be used. A spring or other positive closingdevice may be used to force the door downward in the direction of arrow114 to a closed position or to close a hinged door. Additionally, anintumescent material may be used in combination with the slideable door.

While the present invention has been illustrated by the description ofembodiments thereof, and while the embodiments have been described inconsiderable detail, it is not intended to restrict or in any way limitthe scope of the appended claims to such detail. Additional advantagesand modifications will be readily apparent to those skilled in the art.The invention is therefore not limited to the specific details,representative apparatus and method, and illustrated examples shown anddescribed. Accordingly, departures may be made from such details withoutdeparting from the scope or spirit of the invention.

What is claimed is:
 1. An across the wall pressure differentialindicating apparatus comprising: a wall duct having first and secondopen ends, first and second mounting plates respectively attached to thewall duct at the first and second open ends respectively, a low speedairflow indicator adapted to indicate a pressure differential andmounted in fluid communication with the wall duct such thatsubstantially all airflow passing through the wall duct also passesthrough the indicator, and an intumescent material disposed in the wallduct between the first and second ends.
 2. The apparatus according toclaim I wherein the wall duct is an adjustable length wall duct.
 3. Theapparatus according to claim 2 wherein the adjustable length wall ductcomprises two sections wherein a first section is attached to the firstmounting plate and a second section is attached to the second mountingplate and the first section is slidingly disposed in and in sealingengagement with the second section.
 4. The apparatus according to claim1 wherein the airflow indicator comprises: a housing having wallportions defining a planar draft way extending therethrough and a draftinlet port thereto and a draft outlet port therefrom that are alignedwith the plane of and approximate the size of the planar draft way, anelongate vane pivotably suspended from an upper portion of the housingadjacent to the inlet port and disposed transversely of the planar draftway, wherein the elongated vane is pivotally mounted adjacent its upperend for free swinging movement between an at rest vertically disposedposition for zero air flow through the planar draft way to an inclinedposition angled in the direction of air flow through the planar draftway on air flow being induced through the planar draft way, and theelongated vane is proportioned to substantially partition off the planardraft way when the elongated vane is in its at rest position.
 5. Theapparatus according to claim 4 wherein the elongated vane comprises alength of stripping of film thickness dimensions.
 6. The apparatusaccording to claim 5 wherein the length of stripping includesindentations extending longitudinally for holding same against flexure.7. The apparatus according to claim 4 wherein the wall duct is anadjustable length wall duct.
 8. The apparatus according to claim 7wherein the adjustable length wall duct comprises two sections wherein afirst section is attached to the first mounting plate and a secondsection is attached to the second mounting plate and the first sectionis slidingly disposed in and in sealing engagement with the secondsection.
 9. The apparatus according to claim 4 wherein a firstcross-sectional area of the wall duct is substantially greater than asecond cross-sectional area of the opening in the end wall that isattached to one of the mounting plates.
 10. An across the wall pressuredifferential indicating apparatus comprising: a wall duct having firstand second open ends, first and second mounting plates respectivelyattached to the wall duct at the first and second open endsrespectively, a low speed airflow indicator adapted to indicate apressure differential and mounted in fluid communication with the wallduct such that substantially all airflow passing through the wall ductalso passes through the indicator, and a door disposed on the wall ductfor limiting airflow through the wall duct.
 11. The apparatus accordingto claim 10 wherein the wall duct is an adjustable length wall duct. 12.The apparatus according to claim 11 wherein the adjustable length wallduct comprises two sections wherein a first section is attached to thefirst mounting plate and a second section is attached to the secondmounting plate and the first section is slidingly disposed in and insealing engagement with the second section.
 13. The apparatus accordingto claim 10 wherein the airflow indicator comprises: a housing havingwall portions defining a planar draft way extending therethrough and adraft inlet port thereto and a draft outlet port therefrom that arealigned with the plane of and approximate the size of the planar draftway, an elongate vane pivotably suspended from an upper portion of thehousing adjacent to the inlet port and disposed transversely of theplanar draft way, wherein the elongated vane is pivotally mountedadjacent its upper end for free swinging movement between an at restvertically disposed position for zero air flow through the planar draftway to an inclined position angled in the direction of air flow throughthe planar draft way on air flow being induced through the planar draftway, and the elongated vane is proportioned to substantially partitionoff the planar draft way when the elongated vane is in its at restposition.
 14. The apparatus according to claim 13 wherein the elongatedvane comprises a length of stripping of film thickness dimensions. 15.The apparatus according to claim 14 wherein the length of strippingincludes indentation means extending longitudinally thereof for holdingsame against flexure.
 16. The apparatus according to claim 13 whereinthe wall duct is an adjustable length wall duct.
 17. The apparatusaccording to claim 16 wherein the adjustable length wall duct comprisestwo sections wherein a first section is attached to the first mountingplate and a second section is attached to the second mounting plate andthe first section is slidingly disposed in and in sealing engagementwith the second section.
 18. The apparatus according to claim 13 whereina first cross-sectional area of the wall duct is substantially greaterthan a second cross-sectional area of the opening in the end wall thatis attached to one of the mounting plates.